<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .box1 .title1, .box2 .title2 {
            font-size: 30px;
            color: #1b2b68;
        }

        /*.box2 .title2 {*/
        /*    font-size: 30px;*/
        /*    color: #ff0000;*/
        /*}*/
    </style>
</head>
<body>
<!--并集选择器-->
<div class="box1">
    <div class="title1">标题1</div>
</div>
<div class="box2">
    <div class="title2">标题2</div>
</div>
</body>
</html>
